"Back then it was like Camelot," explains Gene Nora Jessen, 81, of the patriarchy that pervaded the Space Race of the 1960s. "Men went off to wars and women were to stay back and be protected."

For Jessen, a member of the Mercury 13, a group of accomplished female pilots who took part in a similarly rigorous medical and physical testing for space as male astronauts in 1959, pre-existing prejudices never hindered any galaxy-bound ambitions. And in Netflix's recently released documentary Mercury 13 by British filmmakers Heather Walsh and David Sington, she and three other surviving participants provide firsthand accounts as the story of their triumphs and plights unfolds.

Commissioned by NASA researcher Dr. William "Randy" Lovelace, and eventually advised and partially financed by Jacqueline Cochran, a trailblazing aviator and cosmetics magnate, The Woman in Space Program began in 1960. Pilot Geraldyn "Jerrie" Cobb was invited to undergo testing at Lovelace's foundation in Albuquerque, New Mexico and soon became the first woman to pass the evaluation. A true revolutionary, when asked during a television interview why it's important for women to go to space, she replied: "It's the same thing as, 'Is there a need for men in space?' I mean, if we're going to send a human being into space, we should send the one most qualified." After Cobb spoke out, more female aviators, from Wally Funk, a 23-year-old flight instructor, to Jane Hart, a 41-year-old mother of eight, underwent the variety of equal parts tenacious and off-kilter trials.

"It was an extremely thorough physical exam, the most thorough I've ever been through," explains Jessen of the week-long series of tests, which were designed before any human ever flew to space. For the women, each day began with an enema, which preceded a variety of physical examinations, from four-hour eye exams and X-rays to swallowing a rubber tube to test their stomach acids, as well as exhaustive exercises such as riding a weighted stationary bicycle, which gradually becoming steeper and steeper, to assess respiration. The activities that skewed more obscure? Those that were meant to simulate the sensations of being in space, from floating in an isolated, lightless 8-foot tank of warm water in an airtight room (Funk did this for over 10 hours, while male astronauts were only monitored in the same chamber for three) to getting ice water shot into their ears to vertigo-inducing effect.

"The ones I didn't particularly care for, I just laughed off," explains Jessen, who was 23 years old at the time. "When you're young and healthy, you just keep going." And in that spirit, instead of resting up as she was instructed to do at the end of each day, she and one of the project's nurses would hit Albuquerque's Old Town for some good old-fashioned revelry. Sarah Ratley, a Mercury 13 member and onetime Power Puff Derby race pilot who was working as an AT&T electrical engineer when she was recruited by Lovelace, had a similar perspective. "They didn't know exactly what they were looking for, but my attitude was that the whole thing was a big adventure," explains the 84-year-old, adding that she quit her job to seize the opportunity of a lifetime. "I was going to do my best and just see what was next." But while the majority of the women passed the screenings, and in some instances outperformed their male counterparts, their journey to space, regrettably, ended there.

For one, the Mercury Seven men (or the "cookie-cutter males" as Ratley refers to them) were considered better candidates because they were previously test pilots for military jets, a career feat that would have been impossible given that women were barred from Air Force training schools. And then there was the abounding gender bias, most notoriously the concern that a woman wouldn't be fit to fly if she was menstruating, that stemmed from the media, inner workings of NASA, and social constructs of the time. Seeking justice, Cobb and Hart captured national attention when they went in front of Congress to testify against NASA as victims of sexual discrimination, arguing that they weren't afforded the same opportunities in aviation as men. Shockingly, Cochran, previously the women's ally, undermined their testimony saying their going to space could have potential negative effects on the program, as well as family life, while astronaut and national hero John Glenn testified: "The fact that women are not in this field is a fact of our social order." This sentiment was further echoed in a TV clip from 1963, the same year that Soviet cosmonaut Valentina Tereshkova became the first woman to fly in space, in which Mercury astronaut Gordon Cooper is asked during a press conference if women should be a part of the American space program. "Well, we could have used a woman on the second orbital Mercury Atlas that we had," he said. "We could have put a woman up [..] and flown her instead of the chimpanzee." His retort met with droves of laughter.

In 1982, twenty years after the Mercury 13 went to bat for women's rights, Sally Ride, who dealt with plenty of strife herself, became the first American woman and third woman in history to fly to space. But it wasn't until Eileen Collins became the first female pilot of a shuttle mission in 1995 that the group felt truly redeemed. "We were happy for Sally Ride, but we were elated when Eileen Collins went as a pilot," says Jessen. "We didn't just want women to be mission specialists—we're capable of making command decisions, too." And while the surviving members of Mercury 13 have a tendency to downplay their significant role in paving the way for women in aviation, to Earth's skies and beyond, they do recognize the hope they instilled in every generation that followed. "A plane doesn't know or care if it's a man or woman who's flying it," explains Jessen. "We helped create that baseline."